/*
 * QEMU BOOTP/DHCP server
 *
 * Copyright (c) 2004 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#include "slirp/slirp.h"

/* XXX: only DHCP is supported */

#define NB_ADDR 16

#define START_ADDR 15

#define LEASE_TIME (24 * 3600)

typedef struct {
        uint8_t allocated;
        uint8_t macaddr[6];
} BOOTPClient;

BOOTPClient bootp_clients[NB_ADDR];

static const uint8_t rfc1533_cookie[] = {RFC1533_COOKIE};

static BOOTPClient *get_new_addr(struct in_addr *paddr) {
        BOOTPClient *bc;
        int i;

        for (i = 0; i < NB_ADDR; i++) {
                if (!bootp_clients[i].allocated)
                        goto found;
        }
        return NULL;
found:
        bc = &bootp_clients[i];
        bc->allocated = 1;
        paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
        return bc;
}

static BOOTPClient *find_addr(struct in_addr *paddr, const uint8_t *macaddr) {
        BOOTPClient *bc;
        int i;

        for (i = 0; i < NB_ADDR; i++) {
                if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
                        goto found;
        }
        return NULL;
found:
        bc = &bootp_clients[i];
        bc->allocated = 1;
        paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
        return bc;
}

static void dhcp_decode(const uint8_t *buf, int size, int *pmsg_type) {
        const uint8_t *p, *p_end;
        int len, tag;

        *pmsg_type = 0;

        p = buf;
        p_end = buf + size;
        if (size < 5)
                return;
        if (memcmp(p, rfc1533_cookie, 4) != 0)
                return;
        p += 4;
        while (p < p_end) {
                tag = p[0];
                if (tag == RFC1533_PAD) {
                        p++;
                } else if (tag == RFC1533_END) {
                        break;
                } else {
                        p++;
                        if (p >= p_end)
                                break;
                        len = *p++;

                        switch (tag) {
                        case RFC2132_MSG_TYPE:
                                if (len >= 1)
                                        *pmsg_type = p[0];
                                break;
                        default:
                                break;
                        }
                        p += len;
                }
        }
}

static void bootp_reply(struct bootp_t *bp) {
        BOOTPClient *bc;
        struct SLIRPmbuf *m;
        struct bootp_t *rbp;
        struct sockaddr_in saddr, daddr;
        struct in_addr dns_addr;
        int dhcp_msg_type, val;
        uint8_t *q;

        /* extract exact DHCP msg type */
        dhcp_decode(bp->bp_vend, DHCP_OPT_LEN, &dhcp_msg_type);

        if (dhcp_msg_type == 0)
                dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */

        if (dhcp_msg_type != DHCPDISCOVER && dhcp_msg_type != DHCPREQUEST)
                return;
        /* XXX: this is a hack to get the client mac address */
        memcpy(client_ethaddr, bp->bp_hwaddr, 6);

        if ((m = m_get()) == NULL)
                return;
        m->m_data += if_maxlinkhdr;
        rbp = (struct bootp_t *)m->m_data;
        m->m_data += sizeof(struct udpiphdr);
        memset(rbp, 0, sizeof(struct bootp_t));

        if (dhcp_msg_type == DHCPDISCOVER) {
        new_addr:
                bc = get_new_addr(&daddr.sin_addr);
                if (!bc)
                        return;
                memcpy(bc->macaddr, client_ethaddr, 6);
        } else {
                bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);
                if (!bc) {
                        /* if never assigned, behaves as if it was already
                           assigned (windows fix because it remembers its address) */
                        goto new_addr;
                }
        }

        saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);
        saddr.sin_port = htons(BOOTP_SERVER);

        daddr.sin_port = htons(BOOTP_CLIENT);

        rbp->bp_op = BOOTP_REPLY;
        rbp->bp_xid = bp->bp_xid;
        rbp->bp_htype = 1;
        rbp->bp_hlen = 6;
        memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);

        rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
        rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */

        q = rbp->bp_vend;
        memcpy(q, rfc1533_cookie, 4);
        q += 4;

        if (dhcp_msg_type == DHCPDISCOVER) {
                *q++ = RFC2132_MSG_TYPE;
                *q++ = 1;
                *q++ = DHCPOFFER;
        } else if (dhcp_msg_type == DHCPREQUEST) {
                *q++ = RFC2132_MSG_TYPE;
                *q++ = 1;
                *q++ = DHCPACK;
        }

        if (dhcp_msg_type == DHCPDISCOVER || dhcp_msg_type == DHCPREQUEST) {
                *q++ = RFC2132_SRV_ID;
                *q++ = 4;
                memcpy(q, &saddr.sin_addr, 4);
                q += 4;

                *q++ = RFC1533_NETMASK;
                *q++ = 4;
                *q++ = 0xff;
                *q++ = 0xff;
                *q++ = 0xff;
                *q++ = 0x00;

                *q++ = RFC1533_GATEWAY;
                *q++ = 4;
                memcpy(q, &saddr.sin_addr, 4);
                q += 4;

                *q++ = RFC1533_DNS;
                *q++ = 4;
                dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
                memcpy(q, &dns_addr, 4);
                q += 4;

                *q++ = RFC2132_LEASE_TIME;
                *q++ = 4;
                val = htonl(LEASE_TIME);
                memcpy(q, &val, 4);
                q += 4;

                if (*slirp_hostname) {
                        val = strlen(slirp_hostname);
                        *q++ = RFC1533_HOSTNAME;
                        *q++ = val;
                        memcpy(q, slirp_hostname, val);
                        q += val;
                }
        }
        *q++ = RFC1533_END;

        m->m_len = sizeof(struct bootp_t) - sizeof(struct ip) - sizeof(struct udphdr);
        udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
}

void bootp_input(struct SLIRPmbuf *m) {
        struct bootp_t *bp = mtod(m, struct bootp_t *);

        if (bp->bp_op == BOOTP_REQUEST) {
                bootp_reply(bp);
        }
}
